Use of chlorhexidine‐impregnated patch at pin site to reduce local morbidity: the ChIPPS Pilot Trial

Abstract

Pin tract infection is one of the most common complications associated with the use of external fixation. While some studies have identified the potential benefit of chlorhexidine gluconate‐impregnated polyurethane dressings to reduce the incidence of catheter‐related bloodstream infections, we are unaware of any published studies that evaluate the effectiveness of similar technologies in reducing the risk for external‐fixation‐related pin tract infections. Therefore, the purpose of this study was to evaluate the effectiveness of chlorhexidine gluconate‐impregnated polyurethane dressing in reducing percutaneous‐device‐related skin colonisation and local infections. In this initial retrospective cohort, data were abstracted for two groups of consecutive patients undergoing surgery involving external fixation at an interdisciplinary foot and ankle surgical unit. All patients received surgical treatment of their foot/ankle pathology along with application of a hybrid external fixator. Twenty patients (45% male, age 54·5 ± 3·69 years) received chlorhexidine gluconate‐impregnated polyurethane dressing and twenty (55% male, age 55·8 ± 3·22 years) received standard pin care. There was a significantly higher rate of pin tract infection in patients who received standard pin care compared with those who received chlorhexidine gluconate‐impregnated polyurethane dressings (25% versus 0%, P = 0·047). There was no significant difference in any of the descriptive study characteristics (age, gender, diabetes and presence of neuropathy). The results of this initial study suggest that chlorhexidine gluconate‐impregnated polyurethane dressing may be effective to reduce the incidence of pin tract infections and help decrease morbidity associated with external fixation.

Introduction

External fixation is commonly used in the treatment of traumatic fractures, Charcot deformity, limb lengthening, symptomatic non union, malalignment correction and numerous other congenital and musculoskeletal conditions 1, 2, 3, 4, 5, 6, 7, 8, 9, 10. Many advances over the years have been made in both the design and the use of external fixators. Unfortunately, pin tract infections are still commonly associated with external fixation. A potential portal is created for infection whenever the integument is breached by external fixation pins, rods and wires (11). Microorganisms readily transverse the instrumentation tracts, yielding infection incidence rates up to 40% 12, 13, 14, 15, 16. Even higher rates are likely to be present in immunocompromised populations suffering from diabetes, vascular disease and end‐stage renal disease 17, 18, 19. These infections present numerous challenges to patients and caregivers. Infections incur increased risk for morbidity, revisional surgery, extended hospitalisation and commensurate cost of care for patients and health care systems. They can also negate the intended benefit of external fixation by loosening pins and necessitating precipitous extraction of the fixators 11, 12, 13. Interventions developed to combat these infections include the development of tobramycin‐impregnated poly‐methyl methacrylate (PMMA) pin sleeves (20) and formulation of anti‐infective external fixator pins, such as those coated with silver 21, 22, hydroxyapatite 23, 24, 25 and a combination of hydroxyapatite/chlorhexidine (26), to help decrease bacterial colonisation. There has been, however, very little work evaluating the efficacy of intervention in this area in a robust model.

We are unaware of any published studies that evaluate the ability of chlorhexidine gluconate‐impregnated polyurethane dressings (BIOPATCH^® Antimicrobial Dressing; Johnson & Johnson, New Brunswick, NJ) to reduce external‐fixation‐related pin tract infections. Chlorhexidine gluconate‐impregnated dressings are designed to protect against percutaneous‐device‐related skin colonisation and local infections. The dressings are disc‐shaped pieces of foam with a central fenestration and a side slit to facilitate application around external fixation pins and wires. The dressings have previously been shown to significantly reduce the incidence of catheter‐related bloodstream infections and local infections 27, 28, 29. They have been shown in vitro to be effective against methicillin‐resistant Staphylococcus aureus, vancomycin‐resistant Enterococcus, Pseudomonas aeruginosa, Candida albicans and a variety of antibiotic‐resistant clinical isolates (11). The purpose of this study was to evaluate the effectiveness of chlorhexidine gluconate‐impregnated polyurethane dressing to reduce the external fixation device‐related skin colonisation and local infections.

Methods

This study was a single centre, single surgeon retrospective cohort study conducted on 40 consecutive patients presenting for foot and ankle surgery requiring the use of a hybrid external fixator from January 1999 to March 2002. Data were abstracted for two groups of patients. This pre‐ and post‐test design examined a convenience sample of 20 consecutively seen patients who received standard pin care versus a convenience sample of 20 consecutively seen patients who received chlorhexidine gluconate‐impregnated polyurethane dressing after the technology became available to the medical facility and the surgeon.

Standard pin care included the application of triple antibiotic ointment (neomycin, polymyxin and bacitracin) to pin sites 30, 31, 32 twice daily until the 12‐week endpoint. Intervention patients received only chlorhexidine gluconate‐impregnated polyurethane dressing, without the use of antibiotic ointment. The chlorhexidine gluconate‐impregnated polyurethane dressing was applied at the time of surgery and changed weekly until the 12‐week endpoint. Postoperative pin tract infection was clinically determined by the surgeon and defined as pin site erythema extending >2 cm beyond the pin portal with or without drainage.

All patients received surgical treatment of their foot/ankle pathology along with application of the same brand hybrid external fixator. All surgeries were performed by one surgeon at the same medical facility. Outcomes evaluated included proportion of individuals diagnosed with pin tract infection at 12 weeks postoperatively.

Statistical analysis included a Fisher’s exact test to evaluate the differences in proportions for the main outcome measure as well as differences in potential confounding variables, such as gender, diabetes prevalence, neuropathy and use of internal fixation. An independent t‐test was used to assess the differences in potential confounding continuous variables, such as age.

Results

Descriptive characteristics for patients who received standard pin care and chlorhexidine gluconate‐impregnated polyurethane dressing are summarised in 1, 2 respectively.

Table 1.

Descriptive characteristics of patients who received standard pin care

Gender	Age (years)	RA	HIV/AIDS	Cancer	DM	Neuropathy	Immunosupressive medications	Diagnosis	Procedure	Pin tract infection
Female	65	No	No	No	Yes	Yes	No	NU Ankle valgus	Ankle subtalar joint fusion	No
Female	65	No	No	No	Yes	Yes	No	NU ankle fusion	Ankle subtalar joint fusion	No
Female	73	No	No	No	Yes	Yes	No	Midfoot Charcot	Midfoot fusion	Yes
Male	66	No	No	No	No	Yes	No	Midfoot/RF Charcot	Triple arthrodesis + midfoot fusion	Yes
Female	58	No	No	No	Yes	Yes	No	Ankle/RF Charcot	Pantalar arthrodesis	No
Male	49	No	No	No	No	No	No	NU flatfoot repair	Triple arthrodesis with bone graft	No
Male	47	No	No	No	Yes	Yes	No	Failed Charcot repair	Triple arthrodesis	No
Male	74	No	No	No	Yes	Yes	No	Infected ankle/RF fusion	Tibial calcaneal fusion	No
Female	61	No	No	No	Yes	Yes	No	Midfoot/RF Charcot	Triple arthrodesis/midfoot fusion	Yes
Male	58	No	No	No	No	No	No	Pilon and calcaneal Fx	Reduction calcaneal/Pilon fracture	No
Female	70	No	No	No	Yes	Yes	No	Plantarflexed first metatarsal, equinus	First metatarsal osteotomy, TAL	Yes
Male	59	No	No	No	Yes	Yes	No	Midfoot/RF Charcot	Triple arthrodesis and midfoot fusion	No
Female	50	No	No	No	Yes	Yes	No	Infected midfoot Charcot	Fusion of midfoot	No
Female	51	No	No	No	Yes	Yes	No	Ankle/RF Charcot	Pantalar fusion	No
Male	70	No	No	No	No	No	No	NU Ankle/RF fusion	Ankle and subtalar fusion	No
Male	48	No	No	No	Yes	No	No	NU triple arthrodesis	Triple arthrodesis	No
Male	25	No	No	No	No	No	No	Coalition	Triple arthrodesis with bone graft	Yes
Male	34	No	No	No	No	No	No	Open LisFranc’s Fx	Reduction of LisFranc’s fracture	No
Female	27	No	No	No	Yes	No	No	Ankle arthritis	Ankle arthrodesis	No
Male	66	No	No	No	Yes	Yes	No	Ankle/RF Charcot	Pantalar arthrodesis	No

AIDS, acquired Immunodeficiency; AVN, avascular necrosis; DM, diabetes mellitus; Fx, fracture; HIV, human immunodeficiency virus; MU, malunion; NU, non union; RA, rheumatoid arthritis; RF, rearfoot; TAL, tendoachilles lengthening.

Table 2.

Descriptive characteristics of patients who received chlorhexidine patch

Gender	Age (years)	RA	HIV/AIDS	Cancer	DM	Neuropathy	Immuno‐supressive medications	Diagnosis	Procedure	Pin tract infection
Female	29	No	No	No	Yes	Yes	No	RF Charcot	Subtalar joint fusion	No
Male	57	No	No	No	Yes	Yes	No	Ankle/RF Charcot	Pantalar arthrodesis	No
Female	66	No	No	No	No	Yes	No	NU, LisFranc’s Fx	Midfoot fusion	No
Male	55	No	No	No	Yes	Yes	No	Ankle/RF Charcot	Pantalar arthrodesis	No
Female	74	No	No	No	No	Yes	No	Infected ankle/RF Charcot	Triple arthrodesis with midfoot fusion	No
Female	74	No	No	No	Yes	Yes	No	Charcot foot	Midfoot fusion with gastroc recession	No
Male	25	No	No	No	No	No	No	LisFranc’s Fx	Reduction of LisFranc Fx	No
Male	19	No	No	No	No	No	No	MU, Calcaneal Fx	Triple arthrodesis with bone grafts	No
Male	54	No	No	No	No	No	No	Pilon fracture	Ankle with subtalar fusion	No
Female	58	No	No	No	Yes	Yes	No	Ankle/RF Charcot	Pantalar arthrodesis	No
Female	45	No	No	No	No	No	No	LisFranc’s/met Fx	Reduction of LisFranc’s/metatarsal Fx	No
Female	62	No	No	No	No	No	No	RF coalition	Triple arthrodesis with bone graft	No
Female	64	No	No	No	No	No	No	RF coalition	Triple arthrodesis with bone graft	No
Female	65	No	No	No	No	No	No	RF AVN	Triple arthrodesis with bone graft	No
Male	69	No	No	No	No	No	No	NU ankle fusion	Ankle and subtalar fusion	No
Male	39	No	No	No	Yes	Yes	No	RF coalition	Triple arthrodesis with bone graft	No
Female	40	No	No	No	Yes	Yes	No	Midfoot Charcot	Midfoot fusion	No
Female	73	No	No	No	Yes	Yes	No	Failed ankle Fx repair	Ankle and subtalar joint fusion	No
Male	51	No	No	No	Yes	Yes	No	Ankle/RF Charcot	Ankle subtalar joint fusion	No
Male	59	No	No	No	No	No	No	Ankle arthritis	Ankle subtalar joint fusion	No

AIDS, acquired Immunodeficiency; AVN, avascular necrosis; DM, diabetes mellitus; Fx, fracture; HIV, human immunodeficiency virus; MU, malunion; NU, non union; RA, rheumatoid arthritis; RF, rearfoot.

In the standard pin care group, nine patients had Charcot neuroarthropathy, one of whom had an infection; two patients had trauma/fracture, one of whom had an open fracture; five patients had non union; one patient had a rearfoot coalition; one patient had ankle arthritis; one patient had plantarflexed first metatarsal with equinus and one patient had an infected ankle and rearfoot fusion. Of these, two patients had infection (one Charcot patient and one infected with ankle/rearfoot fusion) and one had an open fracture, making a total of three patients in the standard of care group who were at greater risk for pin tract infection. Although these three patients in the standard pin care group were at higher risk for developing pin tract infections, none had clinical signs and symptoms of pin tract infections.

In the chlorhexidine patch group, eight patients had Charcot neuroarthropathy, one of whom had an infection; two patients had non union; one patient had a malunion; four patients had trauma/fracture, one of whom had a failed fixation; three patients had rearfoot coalition; one patient had avascular necrosis from a burn injury and one patient had ankle arthritis. Of these, one Charcot patient had infection and one patient had a burn injury, making a total of two patients who were at greater risk for pin tract infection. Although these two patients in the chlorhexidine patch group were at higher risk for developing pin tract infections, none of them had clinical signs and symptoms of pin tract infections.

The number of patients who were at higher risk for developing pin tract infections between the standard pin care group and the chlorhexidine group was not statistically significant (P > 0·05). The diagnosis category distribution for each treatment group is summarised in Table 3.

Table 3.

Diagnosis category distribution for each treatment group^*

Group	n	Age (years)	Gender (% male)	Charcot (%)	Trauma fracture (%)	Non union, malunion (%)	Coalition (%)	Arthritis (%)	Increased risk of pin tract infection† (%)
Total	40	55·1 ± 5·79	50	42·5	15	20	10	5	12·5
Std care	20	55·8 ± 3·22	55	45	10	25	5	5	15
CHG dsg	20	54·5 ± 3·69	45	40	20	15	15	5	10

CHG dsg, chlorhexidine gluconate‐impregnated polyurethane dressing; Std care, standard pin care.

^* Data are mean ± SD.

^† The percentage is calculated from diagnoses such as open fracture, Charcot foot infection and burns that may increase the risk of pin tract infections. None of these patients had pin tract infections.

Descriptive characteristics for this population are summarised in Table 4. Five patients who received standard pin care and none of the patients who received chlorhexidine gluconate‐impregnated polyurethane dressing developed pin tract infections. Fisher’s exact test comparing infection rates between the two groups revealed that the patients who received standard pin care had a significantly (P = 0·047) higher rate of pin tract infection than those who received chlorhexidine gluconate‐impregnated polyurethane dressings (25% versus 0%). There were no significant differences found among potential confounding variables such as age, gender, diabetes, use of internal fixation and the presence of neuropathy.

Table 4.

Population descriptive characteristics^†

Group	n	Age (years)	Gender (% male)	RA (%)	HIV (%)	DM (%)	Cancer (%)	Organ transplant (%)	Peripheral neuropathy (%)	Combined use of IF (%)	Pin tract infections (%)
Total	40	55·1 ± 5·79	50	0	0	57·5	0	0	60	87·5	12·5
Std care	20	55·8 ± 3·22	55	0	0	70	0	0	65	80·0	25*
CHG dsg	20	54·5 ± 3·69	45	0	0	45	0	0	55	95	0

CHG dsg, chlorhexidine gluconate‐impregnated polyurethane dressing; DM, diabetes mellitus; HIV, human immunodeficiency virus; IF, internal fixation; RA, rheumatoid arthritis; Std care = standard pin care.

^* P < 0·05.

^† Data are mean ± SD.

Discussion

Stabilisation and osteosynthesis using external fixation have proven to be a useful technique for surgeons treating injuries and deformities of the foot and ankle. While very useful, it is not without its complications. Pin tract infections still remain one of the most common complications associated with the use of this technique. Bacterial cultures have demonstrated that most pins are colonised, predominantly with aerobic, Gram‐positive cocci but also yielding Gram‐negative and Candida species 13, 33. In this initial retrospective cohort (pre and post design) study comparing the proportion of individuals diagnosed with pin tract infection at 12 weeks postoperatively in individuals receiving standard pin care versus chlorhexidine gluconate‐impregnated polyurethane dressing, the results suggested that chlorhexidine gluconate‐impregnated polyurethane may be efficacious to reduce the incidence of pin tract infections.

Chlorhexidine is a common component of surgical scrub and skin cleansers. Previous research has demonstrated chlorhexidine to be a more effective antibiotic in both the orthopaedic and the vascular operating environments than povidone–iodine and other antimicrobial agents 34, 35, 36, 37. A decreased number of bacterial colonies were isolated following the use of chlorhexidine versus other scrubs 35, 36. Further research demonstrated that the reduction in bacterial count associated with chlorhexidine is amplified with repetitive use; however, there is no such effect with either povidone–iodine or hexachlorophene (38). W‐Dahl and Toksvig‐Larsen found that surgical patients whose pin sites were cleansed with chlorhexidine had significantly less painful and less frequent pin tract infections require the use of antibiotics than patients whose pin sites were cleansed with saline (13).

Chlorhexidine is a cationic biguanide that acts as a broad‐spectrum antibacterial and antifungal agent. Chlorhexidine works by disrupting microbial cell membranes, resulting in the loss of cell contents (39). The strong attraction of the cationic compound to negatively charged bacterial cells results in an effective antimicrobial agent (11). Chlorhexidine gluconate has demonstrated minimal to zero dermal absorption and an excess of 25 years of clinical experience and laboratory testing have shown it to be safe and effective (34). It is non toxic, is non irritating, and has a low sensitisation potential. It is therefore often the antimicrobial of choice, especially in patients allergic to iodine.

The chlorhexidine gluconate‐impregnated polyurethane dressings used in this study contained 250 μg of chlorhexidine gluconate per milligram of disc dressing. Previous work has shown that an extensive amount of the chlorhexidine gluconate contained within these polyurethane foam discs is continuously released for up to 7 days (34), which significantly reduces the time, energy and money invested in the care of external fixation. A disc weighing 340 mg would release approximately 20 000 μg of chlorhexidine gluconate during a 7‐day period with optimal conditions. Chlorhexidine gluconate‐impregnated polyurethane dressings have demonstrated a 100‐fold decrease in microbial populations beneath the dressing compared with non medicated patches (34). In addition, the residual effect of chlorhexidine upon the skin would actually result in a cumulative zone of inhibition around the foam disc dressing that extends beyond the circumference of the disc.

One inherent limitation to this pre‐ and post‐retrospective cohort study is the lack of formalised randomisation, which may bias the results of the study. This is in concordance with other similar type studies, where there are limitations to historical data and possible secular changes in care. The time dimension of when the chlorhexidine‐impregnated patch technology became available to the medical facility and hence the surgeon is a determinant in patient selection. The control group was a convenience sample of 20 consecutively seen patients who received standard pin care, and the chlorhexidine group was a later convenience sample of 20 consecutively seen patients who received the chlorhexidine‐impregnated patch.

Another inherent limitation of this pre‐ and post‐retrospective cohort study is the lack of quantitative cultures and formal laboratory testing to ensure the diagnosis of pin tract infection. Postoperative pin tract infection in this case was clinically determined by the surgeon and defined as pin site erythema extending >2 cm beyond the pin portal with or without drainage. Future prospective trials in this area could be enhanced by a more precise pin tract infection criteria and definition.

This study is strengthened by the single centre, single surgeon design using the same brand external fixator. It is unlikely that the surgical technique or threshold to use antibiotics changed over this period. We acknowledge that the examiner for infection was not blinded nor extrinsic to the research team. We also acknowledge that there was a trend towards higher mean age and diabetes prevalence in the standard care group that was not statistically significant.

The results of this initial study suggest that chlorhexidine gluconate‐impregnated polyurethane dressing may be efficacious to reduce the incidence of pin tract infections. Chlorhexidine gluconate‐impregnated polyurethane is a once per week dressing that may significantly decrease the time, effort and cost of daily pin site care (30). It may therefore proven to be a simple, economic solution to prophylactically reduce the incidence of pin tract infections and help decrease morbidity associated with external fixation. We await the completion of further studies and trials in this area to confirm or refute this initial assessment.